2015 Colinet et al ANN REV ENTOMOL.pdf


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Annu. Rev. Entomol. 2015.60:123-140. Downloaded from www.annualreviews.org
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EN60CH07-Colinet

ARI

26 November 2014

12:40

a

b

c

d

e

f

g

h

Figure 3
The diversity of fluctuating temperature (FT) treatments. (a) Two temperatures alternating around a constant mean (continuous green
line). These protocols use rapid step transitions. (b) Interruption of a prolonged cold stress (blue) by repeated bouts at optimal
temperature ( green). (c) Repeated exposures to damaging temperatures simulating the effect of heat (red ) and cold (blue) waves. In
panels b and c, the dashed green line represents the optimal temperature. (d ) Multiple step transitions regime around a mean ( green
line) used to simulate complex diel cycles or nature-mimicking thermoperiods. (e) FTs with controlled gradual transitions (ramp)
around a mean ( green line). ( f ) Sine-like wave thermal cycles (night-days) can be symmetric or asymmetric around a mean ( green line).
( g) Stochastic sinusoidal or diel thermal variations. (h) Field temperature variations. For all these treatments (panels a–g), different
amplitudes (dotted black lines), durations, and frequencies of temperature breaks can be applied.

(8, 64). Fortunately, these cues are often synchronized with temperature cycles, so laboratory
procedures can fairly easily reproduce this synchronicity (e.g., 126).

EFFECTS OF FTs ON LIFE HISTORY TRAITS AND FITNESS
Development
Fluctuating temperatures that extend to deleterious high or low temperatures can allow development outside the temperatures where it would normally occur (37, 46, 76, 90). However, FTs
using deleterious temperatures generally delay development compared with development at optimal CTs (46, 63). These delays are likely a consequence of direct cold or heat injuries and of
the costs of subsequent physiological and biochemical repair (24, 43). By contrast, FTs that remain within the permissive thermal range can result in diverse responses, including accelerated
development (2, 13, 44, 65, 66), slower development (25, 42, 66), or no change in developmental
rate (65). One explanation of this variation in responses is that the effect of FTs on the development may depend on the thermal mean that is used and its proximity to developmental thresholds
(65). Accelerated development appears to be the norm if the lower temperature of the FT is not
injurious but falls below a species’ thermal threshold for development (93). Finally, the effect of
FTs on development time also depends on the amplitude of the variation (14, 42, 46, 66), likely
because of Jensen’s inequality. For example, Aedes aegypti mosquitoes reached pupation four days
faster when reared under large (18.6◦ C), rather than small (7.6◦ C), daily FTs (14).

128

Colinet et al.